There are 5 people who need to sit in a row of chairs. Calculate the number of permutations for each situation below:

A.) There are 5 chairs

B.) There are 6 chairs

C.) There are 4 chairs, but Jack, one of the people, needs to be on either end

D.) There are 5 chairs, but Jack needs to be in the middle

E.) There are 5 chairs, but Jack and Jill, another one of the people, must sit together

F.) There are 5 chairs, but Jack and Jill refuse to sit together